Use a cookie or forms authentication that when not present your pages redirect the user to X page. Just set your cookie and forms authentication to just be good for the session and then have them expire so they will be deleted from the users browser.
You cannot prevent a user from copying the URL from the address bar.
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I will only tell you how to do it, not do it for you.
Unless, of course, you want to hire me to do work for you.
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Read this if you want to know how to get a correct reply for your question:
http://www.catb.org/~esr/faqs/smart-questions.html
^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
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Restricting the user from opening pages
